1. Field of the Invention
The invention relates to a hydraulic fluid pump, in particular of a vehicle brake system, having a housing, a piston supported axially displaceably in the housing in a piston chamber, a drive moving the piston, and a sealing element sealing off the piston chamber from the drive. The invention also relates to a vehicle brake system having such a hydraulic fluid pump, and to a sealing element of a hydraulic fluid pump, which element is provided for insertion into a piston chamber of a housing of the hydraulic fluid pump, in which a piston is supported axially movably, which piston is movable by means of a drive.
2. Description of the Prior Art
In known hydraulic fluid pumps of vehicle brake systems, such as those used for instance to return hydraulic fluid during a function as an anti-lock system, pump force housings are embodied in which as a rule two pistons are displaceably supported. Each of the pistons is assigned to one brake circuit. The pistons are displaced axially back and forth by means of a single eccentric drive, and in this way, hydraulic fluid is aspirated into a pressure chamber embodied upstream of the piston and delivered out of that pressure chamber. The pressure chamber is surrounded by its own housing sleeve or a cylinder, which is also sealed off toward the piston. A cylinder and a piston form a so-called pump element, which is inserted into the housing in a stepped bore and is often pressed from outside. The piston protrudes onward into the housing into a region in which the eccentric drive is located at the end. In this region, here called the piston chamber, the supply of hydraulic fluid into the cylinder is also embodied. The annular gap that fundamentally exists between the piston and the housing must be sealed off by means of a sealing element in the form of a sealing ring. Thus the sealing ring seals off between the so-called low-pressure side of the piston and an eccentric chamber that belongs to the eccentric drive.
The sealing rings used, known as O-rings or Q-rings, are usually made from EPDM (ethylene-propylene-diene rubber) and fundamentally have a comparatively good sealing performance. However, in the currently known constructions, as a result of a relative motion between the piston and the sealing ring, a gradual leakage of hydraulic fluid or brake fluid into the eccentric chamber of the eccentric drive nevertheless occurs. Upon increased leakage into the eccentric chamber, the brake fluid can even reach the motor of the eccentric drive, which in some circumstances can damage it and/or lead to its failure.